1. Field of the Invention
The present invention relates generally to a bushing for a jet engine and more specifically to an improved,bushing which is less expensive to manufacture and which facilitates shipping and installation of the bushing.
2. Discussion of the Related Art
Jet engines generally include an axial air compressor which supplies compressed air into a combustor. The front section of a jet engine includes the axial air compressor. The axial air compressor generally includes several consecutive stages, each having a number of stator (stationary) vanes in a shroud and an equal number of rotor (rotating) vanes. Rotor vanes are designed and arranged such that, as the rotor vanes pass by the stator vanes in a particular stage, they take in a volume of air, compress the air and pass this compressed air into the next stage for further compression of the air. Some jet engines, such as the CFM56-2 turbofan engine manufactured by General Electric for example, have thirteen stages of compression. Stages 1 through 5 of this engine have stator vanes in which the pitch of the vanes is variable. The pitch of the variable stator vanes can be adjusted to vary the volume of air intake and thereby control the volume and pressure of the air that is subsequently injected into the combustor to be combined with fuel and ignited. The thrust of the engines can thereby be varied and the amount of air can be metered accurately for maximum fuel consumption. This is desirable because it provides the pilot with greater control over the amount of thrust produced within the engine at given engine speeds. For example, when the pilot is bringing the jet in for a landing, he or she can keep the engine running at very high RPMs and vary the pitch of the vanes to generate less thrust within the engine. If there is a problem and the pilot has to quickly generate thrust to pull up, he or she simply rotates the vanes of the stator to a pitch which increases the amount of air directed into the stator, thus increasing the thrust produced by the engine. The adjustable vanes allow the pilot to quickly produce thrust without having to adjust the RPMs at which the rotor is rotating.
As shown in FIG. 7, each vane 10 of the engine described above includes a blade 12 which is rotatably mounted between an inner shroud 14 and an outer shroud 15. It will be understood that each stator of a jet engine may include several stages, each having many adjustable vanes. However, for simplicity, only one vane is shown in FIG. 7. Vane 10 includes a spindle, partially shown at 16 in FIG. 7 and fully shown at 16 in FIG. 1, which is held in place between portions 20a and 20b of inner shroud 14 within aperture 18. Vane 10 also includes a drive portion 22 mounted within outer shroud 15. A steering mechanism (not shown) is coupled to the drive portion 22 to rotate the vane 10 within the inner shroud 14 and the outer shroud 15.
In order to facilitate the rotation of the vane 10, a bushing is mounted on spindle 16 before it is mounted between portions 20a and 20b of inner shroud 14. A prior art bushing 24 is shown in FIGS. 1 and 2. Since the operating temperature of the jet engine can reach 550xc2x0 F., bushing 24 must be made from a material that can withstand the extremely high temperatures to which it will be subjected. Therefore, bushing 24 is typically formed from a plastic which is capable of withstanding these temperatures. One prior art bushing 24 is formed from a plastic material sold by DuPont under the trademark VESPEL(trademark). However, this material is not capable of being melt processed, meaning that it cannot be used in an injection molding process to form the bushing 24. Bushing 24 is typically formed from a billet of the VESPEL(trademark) material and is machined to the shape shown in FIG. 1, including a circumferential groove 28 (FIG. 2). The bushing 24 is then cut in half to form parts 26a and 26b. An elastic band 30, made from a high temperature-resistant material, is placed within groove 28 to hold parts 26a and 26b together on spindle 16 until the spindle is mounted to inner shroud 14, as described above.
Due to the properties of the material used in the manufacture of bushing 24, the requirement that each bushing be separately machined and the requirement for the elastic band 30, bushing 24 is very time consuming and expensive to manufacture. Shipping the bushings from the manufacturer to the end user is problematic because the three-piece bushings are prone to disassembling during shipping, thus requiring extra time for reassembling the bushing before it is installed on the vane 10. Furthermore, since each part 26a and 26b must be held in place on spindle 16 while the elastic band 30 is installed, the installation of bushing 24 on the vane 10 is very time consuming. Since, every time a jet engine is rebuilt, every vane bushing is replaced, the replacement of the bushings adds considerably to the expense and time required to rebuild an engine.
What is needed is a vane bushing for a jet engine which is simple and inexpensive to manufacture, and which is easy to ship and install on a jet engine vane.
The present invention is directed to a bushing for a jet engine vane which is injection moldable and therefore is simple and inexpensive to manufacture, and is formed into such a design which enables the bushing to. be easily shipped and installed on a jet engine vane.
According to one embodiment of the invention, a vane assembly for an engine is disclosed, the vane assembly comprising a vane comprising a blade having a spindle disposed at one end thereof and a bushing mounted on the spindle. The bushing comprises first and second half portions, each half portion having a generally semicircular body having a first finger disposed at a first end of a first side of the body, a second finger disposed at a second end of the first side of the body and a third finger disposed on a second side of the body, between the first and second ends of the body. The first and second fingers have a distance between them which is not less than a width of the third finger.
The first and second half portions are snap fit onto the spindle of the vane such that the third finger of the second half portion is located between the first and second fingers of the first half portion, and the third finger of the first half portion, is located between the first and second fingers of the second half portion.
Each of the first and second half portions further comprise a semi-annular flange disposed at the first end of the body portion, the semi-annular flange lying in a plane which is substantially perpendicular to a longitudinal axis of the body.
According to another embodiment of the invention, a vane assembly for an engine is disclosed, the vane assembly comprising a vane comprising a blade having a spindle disposed at one end thereof and a cylindrical bushing having first and second portions hingedly attached to each other. The first portion has a first finger disposed at a first end of the bushing and a second finger disposed at a second end of the bushing, the second portion having a finger disposed at a point between the first and second ends of the bushing.
The bushing is secured on the spindle by placing one of the first and second portions on the spindle and closing the bushing around the spindle such that the finger of the second portion is located between the first and second fingers of the first portion.
According to yet another embodiment of the invention, a vane assembly for an engine is disclosed, the vane assembly including a blade having a spindle disposed at one end thereof and a bushing having a cylindrical body. The body has a slot which extends from an upper edge of the body to a lower edge of the body and a number of slits which extend from the upper edge of the body to a point between the upper and lower edges of the body, the slot and the number of slits being constructed and arranged to permit the bushing to be temporarily pried open.
The bushing is mounted on the spindle by prying the bushing open at the slot, placing the bushing around the spindle and releasing the bushing, thereby allowing the bushing to encircle the spindle.
According to yet another embodiment, a bushing is disclosed, the bushing including first and second half portions, each half portion having a substantially semicircular body, an upper end, a lower end, a first side and a second side. The first side of the body of each of the first and second half portions have an intermediate finger disposed intermediate the upper and lower ends of the body and the second side of the body of each of the first and second half portions has an upper finger disposed at the upper end of the body and a lower finger disposed at the lower end of the body. The upper and lower fingers having a distance therebetween which is no less than the width of the intermediate finger.
The first and second half portions are constructed and arranged to be snap fit onto a spindle such that the intermediate finger of the first half portion is positioned between the upper and lower fingers of the second half portion and the intermediate finger of the second half portion is positioned between the upper and lower fingers of the first half portion.